In order to solve the problems of power supply capacity improvement and UHVDC power dissipation in Southern Suzhou 500 kV power grid,the first unified power flow controller (UPFC) project applied in 500 kV power gird is put into operation.Based on the application of Southern Suzhou 500 kV power grid UPFC project and the analysis of power flow regulation demand,this paper sorts out the key control performance indexes and control function requirements of UPFC system.Finally,through system commissioning,the control functions and performances of the UPFC are tested,it mainly includes UPFC basic control performance indexes such as steady-state control precision and dynamic response,N-1 emergency power control function,UPFC locking and automatic restarting control function,which are used to test control ability and operation effect of Southern Suzhou 500 kV power grid UPFC project,it accumulates important practice experience and data for the construction of the follow-up engineering and standard establishment.